1. Field of the Invention
The present invention relates to a push-type switching device which turns on/off an electric contact when a moving body moves to a certain position with respect to a movement detection switch.
2.Description of the Prior Art
FIG. 3A is a perspective view of a conventional push-type switching device, generally a. FIG. 3B is a side view of a movement detection switch. In FIG. 3A, reference numeral 1 denotes a movement detection switch and reference numeral 2 denotes a moving body. As seen from FIG. 3A, the movement detection switch 1 is fastened onto the wall of an electric appliance by a fastening flange 14. The moving body 2 moves in a direction of the movement detection switch 1 by a moving mechanism (not shown).
As seen from FIG. 3B, the movement detection switch 1 is provided with a contact piece 11 for turning on/off an electric contact (not shown), a spring 12 for urging the contact piece 11 forward, and connecting terminals 13 connected to the electric contact.
The movement detection switch 1 is on/off controlled in such a manner that when an abutting fragment mounted on the moving body hits on the contact piece 11 of the movement detection switch 1, it pushes to move the contact piece 11, thereby turning on/off the electric contact.
FIG. 4A is a view for explaining the states when the electric contact of the above switching device falls in an ON state and an OFF state.
As described above, in order that the electric contact falls into the ON or OFF state, the abutting fragment 26 is brought into contact with the contact piece 11 so that the contact piece 11 is pushed, and the contact piece 11 must move over a certain distance.
Therefore, when the contact piece 11 moves over the position where the electric contact falls into the ON or OFF state, no problem occurs. But, when the contact piece 11 has moved to the changing point of ON or OFF, "chattering" will occur.
For example, when the contact piece 11 moves due to vibration, as shown in FIG. 4A, the abutting fragment 26 and contact piece 11 are separated from each other so that the ON state of the electric contact becomes the OFF state as illustrated by 1 and 3. Otherwise, they will be brought into contact with each other again, resulting in the ON state as illustrated by 2.
FIG. 5 is an application example of the switching device a. For example, in a motor driving circuit b, for an electric vehicle, the switching device a is arranged between a battery 41 and an axle shaft driving motor 42, and is used to interrupt the circuit b manually in battery exchange or motor malfunction.
Specifically, in a switch box 43, the switching device is used as a switch 44.sub.3 for a pilot lamp 46 which informs a driver of whether the box 43 is ON or OFF by an indicator 45 in a meter. This switch 44.sub.3 is used in mechanical synchronism with the motor switches 44.sub.1 and 44.sub.2. Therefore, the chattering in the switching device a must be prevented.